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A Brief History of Time-Based Effects- Chorus and Flanging (Part 3)

By Chris Loeffler

While often lumped into the category of “Modulation Effects”, or even pitch modulating effects, the technology behind early forms of chorus or flanging effects began by delaying the original audio signal in ingenious ways to achieve various effects such as signal doubling and phase shifting. Usually described as adding movement or shimmer to an instrument, chorus and flanging cover some of the same sonic ground through similar technology but distinctly different approaches.


The Application of Flanger Effects

The flanging effect, named after the rim (flange) of audio tape (more on that in a minute), is based on two (or more) parallel audio signals cycling in and out of phase with each other. The sonic result is a swooshing sound that covers ground as diverse as the metallic shimmer of Police-era Andy Summers, the jet swoosh of Barracuda, and the time traveling phase of Hendrix’s House Burning Down


Through-zero flanging adds an acid-tinged vibe to House Burning Down.

The Technology of Flanger Effects

Flanging originally was achieved through physical manipulation of reel-to-reel recordings to create subtle acceleration and deceleration of one recording played against the other (unaltered). The result is comb filtering and pitch shifting as the tape speeds fall in and out of synch with each other. By feeding the output back into the input, the flange effect is further intensified. The pioneer and first noted use of the effect? Mr. Les Paul in 1945 with Mamie’s Boogie. 


Obviously, studio manipulation of tape couldn’t be replicated in live performance, so the effect was confined to recording until 1974, when flanging was brought to the solid-state world via the Design Technology Flange Delay Line. By 1976, flanging classics Electro-Harmonix Electrtic Mistress, Tychobrahe Pedalflanger, Ibanez FL-305, and T.C. Electronics SCF were on the scene. These pedal and rack effects relied on the same BBD chips used for delay pedals with the delay time modulated between 5-15MS by an internal LFO to recreate the modulating parallel tape signals with a feedback loop, effectively recreating the mechanics of tape flanging. Compared to true tape flanging, analog electronic versions are somewhat less nuanced as they are locked into the perfection of the LFO and exhibit less of the non-linear behavior created by tape manipulation.


As a brief aside, less prominent but certainly worthy of mention is Barber Pole flanging. Rather than modulating in and out of phase synch, Barber Pole flanging only sweeps in a single direction in repeat, creating the sonic effect of a dramatic rise or fall in flange with an abrupt reset of phase.


As with other time based effects, flanging went digital in a big way as digital technology emerged and flanger-esque algorithms were created. The limitations of early digital resolution resulted in even more hollow and metallic tones but shed the confining restrictions of analog technology by introducing longer delay times for more extreme effects and more control over the LFO. Modelling technology, being what it is, has effectively recreated all three previous flanger technologies via software. 


Examples of Flanger Effects and Usage

Classic Analog Flanger- A/DA Flanger, Boss BF-2, EHX Electric Mistress, MXR Flanger

Classic Digital Flanger- Ibanez DFL Digital Flanger, TC Electronic M5000

Classic Modeled Flanger- Line 6 Liqua Flange, Strymon Orbit



The Application of Chorus Effects

The goal of the chorus effect is to create multiple timbres and pitches close, but never identical, to the original signal to achieve the sonic impression of multiple instruments playing the same note. The chorus effect is used to a variety of sonic ends, including thickening up an instrument’s sound, adding animation and harmonic depth, creating watery modulation, and even mimicking the Doppler effect of a rotating speaker.


Classic clean chorus tries its best to wear out its welcome in the 80's


The Technology of Chorus Effects

The original chorus was literally multiple musicians playing the same part at the same time. The slight variances in instrument tone and playing style creates a richer, more complex sound than a single instrument is capable of producing. Like most effects, chorus as an effect began in the studio in the form of combining multiple takes of an instrument, recreating a “chorus” of musicians with a single musician. 


The first chorus effect in electronic form was the Roland CE-1 and relied on BBD technology to create a 4-40MS delayed signal that bended pitch as it modulated toward and away from the original signal. These bucket brigade chips create a parallel signal that is delayed at various times, resulting in the same pitch bend that occurs when the time is increased on a delay pedal. Smaller in focus and rhythymic, the LFO creates a warbled version of the signal that can fatten or add movement to the original, and the antialiasing filters required to tame the circuit rolls off some of the high-end of the signal for a darker, warmer sound.


In electronic form, the Chorus effect shares a lot in common with flanging and vibrato. Whereas the vibrato effect usually relies on pitch modulation of the instrument’s signal, Chorus often (but not always) leaves the direct signal unaffected and pitch modulates the effected signal (usually slightly delayed) against the original signal to achieve the “multiple instruments” impressions. As compared to flanging, electronic chorus effects rely on similar technology but often incorporate longer delay times and eschew the feedback loop and regeneration. Others, such as the Boss Dimension-C, utilize several static delay lines to create a spatial chorus without the modulating pitch.


As an aside, a small but notable diversion from the technology of chorusing that achieved a similar result was Pat Metheny’s divisive use of chorus in his early albums. In these cases, the chorus effect is actually two digital delays panned left and right with 14ms delay on one and a 26 ms delay on the other. The result, even without detuning, is identical to a typical chorus effect created by a pedal.



Examples of Chorus Effects and Usage


Classic Analog Chorus- Roland CE-1, Boss CE-2, TC Electronics SCF, Electro-Harmonix Small Clone

Classic Digital Chorus- Boss CE-5, Eventide Rack

Classic Modeled Chorus- Line 6 MM4, Strymon Ola



Exploring Time-Based Effects (Part 1)

Exploring Time-Based Effects (Part 2)


Chris Loeffler is a multi-instrumentalist and the Content Strategist of Harmony Central. In addition to his ten years experience as an online guitar merchandiser, marketing strategist, and community director he has worked as an international exporter, website consultant and brand manager. When he’s not working he can be found playing music, geeking out on guitar pedals and amps, and brewing tasty beer. 

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